The present invention relates to dental twist drills and more particularly to dental twist drills of the type utilized in conjunction with the anchoring of prefabricated post cores in the tooth canal.
In root canal therapy it is customary to drill a relatively deep hole into the root of the tooth for reception of a post core or anchor therein, the anchor or post core to be subsequently surmounted by a crown. In formation of the deep hole it is extremely important to maintain the side walls of the canal as parallel as possible to insure optimum securement of the post core therein. However, it is commonplace, during drilling of the canal, for the resultant hole to be tapered and for an undesirable enlargement of the opening of the canal to develop. Generally these effects are attributable to movement of the hand of the operator or to wobbling of the handpiece which drives the drill. Systems currently in use employ prefabricated post cores or anchors which are size-correlated with the drill used to form the canal. The post core or anchor achieves retention by virtue of a friction-fit or by a screw thread adjacent to the top of the canal opening. It will thus be appreciated that when a tapered hole is formed the bite of the screw threads into the tooth structure is decreased with consequent diminution of retention of the post core within the canal. In such instances cement is frequently resorted to in an attempt to maximize retention; however, the cement is susceptible to fracture and pulverization which results in loosening of the post core and crown.
One system for the anchoring of prefabricated metal posts into the roots of teeth employing anchors having parallel side walls sized precisely to the diameter of a corresponding uniform diameter twist drill is marketed by Star Dental Mfg. Co., Inc. of Conshohocken, Pennsylvania. Such system is known as the Star Dental Radix-Anchor System. As stated earlier, optimum securement of the Radix-Anchor is enhanced by formation of a parallel-sided canal.